I. Field of the Invention
This invention relates to a system for injecting chemicals into a geothermal well and, in particular, to a spool and injection assembly which allows safe insertion of the injection assembly and internal casing expansion during insertion of the injection assembly through a secondary outlet independent of the master valve.
II. Description of the Prior Art
Geothermal wells produce steam from heated subsurface areas. The wells are drilled and completed utilizing oilwell drilling equipment although techniques differ for such wells including the use of larger well bores, well casings and surface wellhead valves and fittings. Steam from the geothermal wells flow from near the bottom of the well bore through the casing and surface valves in large enough volumes to power turbines for producing electricity. The distinctiveness of producing steam from geothermal wells brings operating complications specific to the geothermal industry that include corrosion problems and the build-up of scale on metal casings and surface valves. This corrosion and scaling faced by the geothermal industry limits the useful life and production capabilities of the geothermal well. In order to control this corrosion, various chemicals have been developed although they must be deployed near the bottom of the well.
The prior known method for entering the well with a chemical injection device capable of injecting chemicals near the bottom of the well involved opening of the master valve and inserting tubing from the surface to the bottom of the well. However, the open condition of the master valve for chemical injection creates a potentially dangerous situation since the master valve cannot be closed without destruction of the injecting tubing or damage to the master valve.